1. Field of the Invention
The present invention relates to a motor-driven power steering apparatus, and more particularly relates to fault diagnosis of a temperature sensor of the motor-driven power steering apparatus used for temperature compensation of a drive motor or the like.
2. Description of the Related Art
In a motor-driven power steering apparatus used as a drive source assisting a steering operation, since the motor-driven power steering apparatus is arranged within an engine room in which an internal combustion engine is arranged and a heat is generated, and the motor itself generates heat, a temperature of the motor is widely variable.
Particularly, if the temperature of the motor is increased so as to become equal to or higher than a predetermined temperature, there is a risk that the motor and a motor drive circuit may be thermally damaged. Accordingly, there has been proposed an example (for example, refer to Japanese Patent Application Laid-Open No. 60-035663 (patent document 1)) in which an operating amount of a motor is reduced in the case that a temperature of the motor is detected and becomes equal to or higher than an allowable value.
In the patent document 1 mentioned above, the temperature of the motor is determined on the basis of an ambient temperature detected by a thermistor arranged near the motor and a temperature increase by driving the motor. Accordingly, if a fault is generated in the thermistor itself, there can be generated a matter that the detected motor temperature is equal to or lower than the allowable value and the operating amount of the motor is not reduced even though the temperature of the motor is actually more than the allowable value, whereby the motor and the motor drive circuit is thermally damaged.